DETROIT— The U.S. automotive sales slump worked its way to Janesville, Wis., today when General Motors Corp. told workers that it would stop making sport utility vehicles at a factory there in December.

GM spokesman Chris Lee said SUV production at the plant, with 1,200 workers represented by the United Auto Workers, will end Dec. 23, earlier than GM had expected.

The Janesville plant also has a small- to medium-duty truck production line with 35 to 50 workers. They will keep working until they have filled an order for Isuzu Motors Ltd., which should take the plant through May or June, Lee said. Then the plant "will cease operations completely," he said.

Workers at the plant will get most of their pay from the company and unemployment benefits for up to two years under their union contract. They will have the option of transferring to other GM factories if jobs are open.

Most of the Janesville factory makes the GMC Yukon and the Chevrolet Tahoe and Suburban large SUVs, and sales of those vehicles have plummeted with an increase in gasoline prices to around $4 per gallon earlier this year. Gas prices have subsided closer to $3 per gallon nationwide, but that has done little to boost sales.

"That segment is really shrinking, so we had to make the difficult decision to have this cessation," Lee said.

A state lawmaker held out hope that GM will get a new product line and stay open.

State Rep. Mike Sheridan, a Janesville Democrat and former plant union representative, said in a statement Monday that GM is still considering whether to bring a line of small cars to the facility.

Lee said those discussions continue but have no bearing on the decision to end SUV production.

GM shares soared $1.61, or 33 percent, to $6.50 in midday trading as markets rose on news that the Bush administration and European governments pledged coordinated actions to help the crippled financial system. The shares had lost nearly half their value last week.

GM announced in June that it would close Janesville and three other factories as demand for pickup trucks and SUVs waned, but the only time frame that was given was by 2010. The company announced earlier this month that another of those plants — the Moraine, Ohio, SUV factory — will close Dec. 23.

On Friday, a person with knowledge of GM's plans said it could close more factories as early as this week to deal with slumping sales and the collapse in its stock price. The announcement was likely to include acceleration of the assembly plant closures, which also include factories in Oshawa, Ontario, and Toluca, Mexico.

The person, who did not want to be identified because the plans are not finalized, said further cuts would likely hit engine, transmission and stamping operations to correspond with the assembly plant closures.

GM Chairman and CEO Rick Wagoner said last month that the automaker would have to make adjustments, particularly in metal stamping factories.

Lee would not comment Monday when asked if further plant closures or announcements are expected.

The Janesville plant opened in 1919 and is GM's oldest. Its closure comes despite an incentive plan offered to GM last month by Wisconsin political leaders.

Suburban, Tahoe and Yukon sales are down by more than 40 percent so far this year, and sales in the large SUV segment are down 49 percent, according to Autodata Corp. GM also makes those vehicles at its plant in Arlington, Texas, and GM officials have said that plant can crank out enough to meet present demand.

Industry analysts say closing factories or cutting shifts will help GM reduce costs and preserve cash at a critical time with the company losing billions and burning up cash at an alarming rate.

GM had $21 billion in cash and $5 billion available through credit lines at the end of June for total liquidity of $26 billion but has been burning up cash at a pace of more than $1 billion a month.

The company announced a plan in July that calls for cutting $10 billion in costs and raising another $5 billion through asset sales and borrowing through 2009.

GM's shares plunged to the lowest level in 59 years last week. The shares fell 31 percent to $4.76 Thursday and dropped to $4 in the first minutes of trading Friday, the lowest level since Nov. 16, 1949, according to the Center for Research in Security Prices at the University of Chicago. They rebounded to end six straight losing sessions and close at $4.89, up 13 cents, or 2.7 percent.

On Friday night, word leaked that GM had talks with Chrysler LLC owner Cerberus Capital Management LP about GM merging with or acquiring Chrysler. The talks have been shelved during the country's financial crisis.